1. Field of the Invention
The present invention relates to an implantable medical apparatus for detecting diastolic heart failure (DHF), of the type having a DHF determining device for determining at least one blood pressure parameter for detecting a DHF state of the heart of a patient. The invention also relates to a pacemaker provided with such an apparatus, and a method of detecting DHF, including the step of determining at least one blood pressure parameter for detecting a DHF state of the heart of a patient.
2. Description of the Prior Art
There is a growing recognition that congestive heart failure caused by a predominant abnormality in the diastolic function, i.e. diastolic heart failure, DHF, is both common and causes significant morbidity and mortality. Therefore early detection of DHF is important. Patients do not, however, seem to have symptoms at an early stage. In addition it has been hard to separate diastolic and systolic heart failure and they may also exist simultaneously.
It has been discovered that among the few parameters, separating diastolic heart failure from systolic heart failure, are certain blood pressure parameters obtained during work of the patient. Thus U.S. Pat. No. 6,438,408 describes an implantable medical device for monitoring congestive heart failure, CHF. A number of heart failure parameters indicative of the state of the heart failure are measured employing EGMs, blood pressures including absolute pressures, developed pressures (=systolic pressures−diastolic pressures) and the time derivative dP/dt, as well as heart chamber volumes. One of these parameters is the relaxation or contraction time constant τ of the heart chamber. This constant τ is calculated from a continuous pressure signal and is the drop in ventricular pressure at the end of systole and in the first part of diastole. The τ parameter is thus a general parameter reflecting the relaxation process.